The present invention relates to an etching system for forming a thin film pattern on a semiconducting substrate, and, more particularly, to a cooling means for cooling an amorphous carbon electrode of an etching system for manufacturing a semiconductor device.
A reactive ion system (RIE) is used in a process of manufacturing semiconductor devices such as LSIs and transistors. Such an etching system etches, by a necessary thickness, the entire area or a specified area of a thin film (metal electrode film or insulating oxide film) formed on the surface of a wafer by the synergistic effect of radicals and reactive ions in a reactive gas plasma. In this etching system, a reactor chamber contains an upper electrode (carbon electrode) made of amorphous carbon and a lower electrode on which a wafer is mounted in such a manner as to face the upper electrode; and a reaction gas such as CH.sub.4, CHF.sub.3 or Ar is supplied in the chamber at a specified pressure. A high frequency power is applied to the carbon electrode in such a state for forming a plasma region between the carbon electrode and the lower electrode, to etch a wafer mounted on the lower electrode by chemical reaction with radicals and reactive ions in plasma. This etching system is provided with a cooling device on the upper portion of the carbon electrode for holding constant the temperature in the reactor chamber and holding constant an etching condition, and a refrigerant (cooling water) controlled at a specified temperature (for example, 25.degree. C.) in a thermostatic chamber (refrigerator) is circulated in the cooling device.
The above etching system, however, has only carried out temperature control of a refrigerant (cooling water) by detecting the refrigerant in a thermostatic chamber and driving the refrigerator so as to hold constant the temperature of the refrigerant, particularly has not carried out temperature control of a carbon electrode at constant temperature. As a result, the above etching system has presented the following inconveniences. Namely, as shown by a line "b" in FIG. 1, when an etching processing time becomes longer, the temperature of the carbon electrode itself is increased by plasma discharge, to increase the supply amount of carbon from the carbon electrode introduced into the plasma. This increases a ratio of deposition of carbon on a wafer, to reduce an etching rate as shown by a line "a" in FIG. 1, causing variations in uniformity and selectivity of etching on the surface of the wafer in a lot. Thus, the etching condition is varied and the film thickness and shape are made non-uniform. This exerts adverse effect on device characteristics.